Writers of Pro Football Prospectus 2008

Extra Points

Are all Denver RB created equal?

Denver's recent trade of Tatum Bell and George Foster for Dre' Bly was just one more example in a long history of discarded Denver running backs. Since Olandis Gary turned in a 1,000-yard season subbing for Terrell Davis in 1999, the Broncos have not had a running back lead the team in rushes for more than two straight seasons. Five different Denver backs -- Gary, Mike Anderson, Clinton Portis, Reuben Droughns, and Bell -- have put up 1,000-yard seasons in that time.

The Broncos clearly realized years before other teams that running backs are often just a product of the system. The Colts just won the Super Bowl after letting Edgerrin James leave in free agency. Shaun Alexander struggled just one season after winning the MVP due to his own injuries and offensive line struggles. The simple truth is that is that more than 30 running backs could run for over 1,000 yards behind a solid offensive line. The Broncos’ realization of this fact has saved them cap space and allowed them to acquire the best pair of corners in football. (Champ Bailey came in a previous trade for Clinton Portis.)

All of the above is true, but the next logical step after "running backs are fungible" is "all running backs are created equal." But this is not necessarily the case. Six different running backs have led the Broncos in rushing the past eight seasons, but they have been far from equal. Here is a look at how each one did in our Football Outsiders advanced stats of DPAR (which measures total value) and DVOA (which measures value per play):

As an aside, Terrell Davis trumps even Portis. He had 59.1 and 65.7 DPAR in 1997 and 1998 respectively, leading the league each year. He also led the league in DVOA in 1998, and was second in 1997, narrowly behind Barry Sanders.

Not surprisingly, given the inconsistent running backs, the Broncos offense has had some wild swings during this period. Despite their sterling reputation, they have had three below average seasons running the football. Here's a look at total offensive DVOA as well as rushing offense for Denver as a team:

The Broncos have had two main quarterbacks during this period, Brian Griese and Jake Plummer. The offensive line has not been consistent outside of Tom Nalen, who has anchored the line during this whole period. Nalen is the only Denver offensive lineman who has made the Pro Bowl during this period.

Maybe uncertainty in the line corresponds with the decreases in effectiveness, but I’d argue that perhaps Mike Anderson and Clinton Portis are better players than the other backs. Tatum Bell was more successful in 2005 than last year, but he was still substantially less productive from a DVOA perspective than Anderson was.

I think the Broncos got the better of the trade with Detroit, but at a certain point, the Broncos may be getting too cute. They are consistently above average, but only once in the past four years (2005) did they have a truly outstanding offense. And yet, they continue with the same strategy.

The next 1,000-yard rusher will likely be the recently signed Travis Henry. Denver signed him to a sizable contract, perhaps realizing that not all backs are created equal. The problem is that Henry has proven himself solid, but below average. He has yet to post a positive DVOA in Buffalo or Tennessee despite multiple 1,000-yard seasons. In general, he has always put up high yardage totals simply because teams kept giving him the ball as the starting running back.

This year, Henry will probably rack up another 1,200 yards or more, and everyone will pat Denver on the back for adding another name to the list of seemingly successful backs they have created. It is far from certain, however, that Henry will be more like Portis than Droughns. Anybody can gain yardage in the Denver system, but not just anyone can be a star.